OBJECTIVES: Use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers results in decreased morbidity among patients with chronic heart failure (CHF). Undersupply of medication could result in inadequate control of CHF, whereas oversupply of medication could increase health-care costs and risks of toxicities. This study aimed to determine the effects of medication supplies on health-care costs and hospitalizations in patients with CHF receiving angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.

METHODS: We retrospectively examined the electronic database in a hospital in Thailand. Patients who were diagnosed with CHF and who received angiotensin-converting enzyme inhibitors or angiotensin receptor blockers in the year 2003 were included. Medication supplies were assessed by using the medication possession ratio (MPR). The Cox proportional hazard model was used to determine the association of medication supply (appropriate supply: MPR 0.8-1.2, oversupply: MPR > 1.2, undersupply: MPR < 0.8) with CHF-related and all-cause hospitalizations. Health-care costs were compared by using multiple linear regressions. All analyses were adjusted for propensity score and other variables.

RESULTS: A total of 393 patients were included. Their mean age was 66 years, with 56% being females. Fifty-seven percent of the patients received an inappropriate -supply of medication. Undersupply of medication likely increased the risks of CHF-related hospitalization with an adjusted hazard ratio of 1.66 (95% confidence interval [CI] 0.80-3.46). The adjusted hazard ratio of undersupply and oversupply of medication for all-cause hospitalization was 1.13 (95% CI 0.74-1.73) and 3.19 (95%CI 0.66-15.47), respectively. The total health-care costs in the undersupply and oversupply groups were significantly greater than that in the appropriate-supply group: $49 (95% CI 32-66) and $103 (95% CI 32-173), respectively.

CONCLUSIONS: Inappropriate medication supplies could increase the risks of CHF-related and all-cause hospitalizations. Both undersupply and oversupply of medication had significantly higher health-care costs.